LITITZ, Pa. – A 14-year-old girl, whose unhinged 18-year-old boyfriend allegedly gunned down her parents in a fight over their illicit affair and then fled with her, stood dazed yesterday as she laid her folks to rest.

Wearing a white sweater and long black skirt, Kara Beth Borden smiled and hugged the nearly 400 friends and relatives attending the funeral service in rural Lancaster County for her parents.

They were brutally slain Nov. 13, allegedly by her boyfriend, David Ludwig. “She’s been dealing with this situation for a few days,” said her lawyer, Robert Breyer. “She’s absolutely in shock about what’s happened.”

The service came as an alarming picture emerged of Ludwig’s downward spiral as he carried on the affair with his underage girlfriend in a deeply religious community and against the wishes of her devoutly Christian family.

Police Chaplain Michael Shelley also revealed yesterday that Ludwig had run off with a girl once before.

Sometime in the spring he took a girl to his family’s hunting cabin in Juniata County, but brought her back voluntarily. The situation was resolved between Ludwig’s family and the girl’s family, police said.

It has also been revealed that Ludwig had an obsession with guns and was videotaped discussing in detail carrying out a brutal murder.

Ludwig is charged with gunning down Borden’s parents, Michael and Cathryn, at their home, then driving off with his girlfriend before police caught up with them in Indiana. He is being held without bail.

In the eyes of those in this idyllic community in central Pennsylvania, the teen lovers were raised to be wholesome and God-fearing, yet thumbed their noses at family, friends, convention and the law.

Friends and neighbors either missed or dismissed the hints of something darker and deadlier.

“I knew he was sneaking into her house in the middle of the night,” Ludwig’s friend, Zach Horvath, told the Lancaster New Era newspaper. “People were getting pretty upset about it.”

Deeply religious and heavily involved in the local church, Michael Borden once gave his younger daughter Katelyn a diamond ring for promising to remain chaste until marriage.

“He would do everything he could to keep her pure until she married,” said the Rev. Rex Trogden at yesterday’s funeral service.

So the pair, who were both home-schooled, tried to keep their budding love a secret. Ludwig often sneaked in and out of her house, and the two of them e-mailed nude pictures of themselves to each other.

At one point, Borden’s parents cut off her Internet access to keep the two from communicating.

Arguments over the relationship occurred frequently. It was during one such fight that Ludwig shot and killed them, cops said.

But his lawyers, James Gratton and Merrill Spahn, say he may not have acted alone, and indicated that Borden may have been involved.

“We have been advised by Mr. Ludwig that the behavior of [Kara Beth] and himself [while on the run] . . . will serve to negate the charge of kidnapping . . . and will be directly relevant to the issue of the involvement of the parties in the charges of homicide,” they wrote in a motion filed Friday.

Borden’s attorney said any thought that she could have been behind the murder of her parents was ridiculous.

“If the cops thought she had anything to do with this, she wouldn’t be at home watching movies, she would be held in detention,” Breyer said.

As the relationship went on, there were changes in the pair, friends recall.

“David was slipping in the last couple of months, drawing back from everyone and putting on a façade,” Horvath said. “Nobody really knew the real David anymore.”

Horvath said friends told him of a particularly startling conversation with Ludwig that took place a day and a half before the murders.

“He had been making comments, ‘Oh, I could kill someone and get away with it, disappear and nobody would find me,’ ” he added.

The chilling claim was a long way from the friendly, outgoing, Christian boy known to many here.

Cristen Frederick, 23, a college student who worked with Ludwig at a Circuit City outlet, said she knew Ludwig and Borden were dating – and keeping it secret because of the age gap.

“He was a really good guy,” she said. “He was friendly and joked around. I considered him to be a good Christian. He brought his Bible and read it during breaks.”

Borden, on the other hand, frequently brushed off friends’ warnings that Ludwig could end up in jail for dating her.

“You don’t know how much we feel about each other and how much we want to be with each other,” Borden told one friend.

But cops say the situation was growing more sinister right beneath everyone’s noses.

In an alarming video file retrieved from Ludwig’s computer, cops say he and a pal, Samuel Lohr, 19, ran through detailed scenarios to conduct an armed raid on another family’s home and kill people inside.

Police said Lohr told them that the aborted break-in featured in the 18-minute video was among several such “late-night armed plans of forcible entry” that he and Ludwig conducted.

In the video, the pair are shown taking guns from Ludwig’s house to a home and discussing using them to “shoot and kill family members inside of the residence,” according to an affidavit.

The movie showed Ludwig and Lohr talking about “Ludwig’s intimate relationship with Kara Borden before deciding to continue their ‘night patrol’ ” by going to the Borden home, the affidavit said.

They also discussed having sex with Kara Beth and her 13-year-old sister, but noted “that the sex would constitute statutory rape,” and Ludwig said he might have to kill someone if anyone found out about it, the affidavit said.

Police seized 54 guns from the home where Ludwig lived with his parents, according to court documents. Ludwig is being held without bail on murder and kidnapping. Borden has not been charged.

“Living inside the devastation of this unimaginably horrible week, no words can adequately express the sorrow, shock and senselessness of what we’re all experiencing,” the Ludwig family said in a statement, declining further comment.

The Ludwigs had lived in the area for about eight years, the Bordens for nine.

Michael Borden worked in printing. Ludwig’s father was an airline pilot and avid gun collector.

The Bordens – including Kara Beth, two older brothers, a younger brother and her younger sister – lived comfortably in a home worth about $300,000.

The Ludwigs bred dogs and encouraged sports and outdoors activities for their children.

Ludwig also was part of a community band, playing saxophone. Borden liked dogs and prayer and played on the youth soccer team.

Tiffany Bomberger, 21, a graduate of the home-school group, knew and liked the pair.

“We were close. We hung out a lot,” she said.

“We would talk and do different things together. I thought he was a great guy. He was smart, friendly and very talented. And he had a high IQ.”

The teens would go snowboarding, and Ludwig mastered the sport in a matter of hours.

In the last five months, they hadn’t talked as much, Bomberger said. She thought it was because he got the job at Circuit City and was trying to be a volunteer EMT.

He was more introverted lately, she said. “But I took that like a lot of teenagers go through things like that.”